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<title>Volcanoes – JOIDES Resolution</title>
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<title>Volcanoes – JOIDES Resolution</title>
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<title>One week at sea and we’re out of bananas</title>
<link>https://joidesresolution.org/one-week-at-sea-and-were-out-of-bananas/?utm_source=rss&utm_medium=rss&utm_campaign=one-week-at-sea-and-were-out-of-bananas</link>
<comments>https://joidesresolution.org/one-week-at-sea-and-were-out-of-bananas/#respond</comments>
<dc:creator><![CDATA[Sara Whitlock]]></dc:creator>
<pubDate>Sun, 25 Dec 2022 08:24:38 +0000</pubDate>
<category><![CDATA[Drilling]]></category>
<category><![CDATA[Expeditions]]></category>
<category><![CDATA[Geochemistry]]></category>
<category><![CDATA[History of Earth]]></category>
<category><![CDATA[Life at Sea]]></category>
<category><![CDATA[Microfossils]]></category>
<category><![CDATA[Paleomagnetism]]></category>
<category><![CDATA[Scientific Outreach]]></category>
<category><![CDATA[Ship's Log]]></category>
<category><![CDATA[Volcanoes]]></category>
<category><![CDATA[EXP398]]></category>
<guid isPermaLink="false">https://joidesresolution.org/?p=39381</guid>
<description><![CDATA[“It’s been three days since I was outside…” I hear as a group whooshes by my desk. My office is... <div class="read-more"><a class="excerpt-read-more" href="https://joidesresolution.org/one-week-at-sea-and-were-out-of-bananas/" title="Continue reading One week at sea and we’re out of bananas">Read more<i class="fa fa-angle-right"></i></a></div>]]></description>
<content:encoded><![CDATA[<p>“It’s been three days since I was outside…” I hear as a group whooshes by my desk. My office is next to the door outside, so I get snippets of conversations as people pass seeking vitamin D.</p>
<p>I’m the outreach officer on a scientific research ship called the <em>JOIDES Resolution</em>, and we’ve been at sea for a week. We sailed from Tarragona, Spain, to a site near Santorini, and we’ve been parked in place for three days, drilling for samples of sediments and rocks—called cores—underneath the ocean.</p>
<p>It’s not that surprising that the scientist passing my office hadn’t been outside for several days. Work on the ship is intense, as researchers try to make the most of the two months they have on board and get as many high-quality core samples as possible.</p>
<p>There are at least two scientists assigned to every role on board, with one working a shift from noon to midnight and the other from midnight to noon. After being on their feet for twelve hours, I see lots of stretches and back adjustments in the galley at mealtimes.</p>
<p>The shifts are long, but every time I hear that they’ve seen something unexpected in the sediment samples, there’s a glint in the scientists’ eyes. This trip is the culmination of years of planning. For some, they’ve been studying the region we’re drilling in for their entire career.</p>
<p>Our mission is to discover a more complete history of the volcanic system around the islands near Santorini. Three submarine volcanoes—Christiana, Kolumbo, and Santorini—make up this system, and they’ve exploded hundreds of times over the last 360,000 years. Most famously, a massive eruption of the Santorini volcano in the Late Bronze Age might have played a role in the decline of the Minoan civilization on nearby Crete.</p>
<p>What we know about these volcanoes comes from studies on land and shallow samples taken under the ocean with a drilling system that uses gravity to plunge into the sea floor. Yet most of the products that linger after one of these volcanoes erupt are deposited onto the nearby sea floor. That record is much older and deeper than what’s been reached so far.</p>
<p>That’s why we’ve brought the aging, but powerful, <em>JOIDES Resolution</em> to the area. The ship is an oil drilling rig converted for scientific research in the early 1980s, and it can pull up core samples of muds and volcanic products from as deep as 5 miles (8km) below the surface of the ocean.</p>
<p>Over the next seven weeks, we’ll use the ship’s drill to push down to 2200 feet (765 meters) below the sea floor and get samples that can extend our understanding of this volcanic system and others like it around the world.</p>
<p>At our first of six drilling sites, work has been smooth. Glassy waters are a welcome relief for those who suffered in the 3m waves on our trip over from Spain. The islands all around us offer—to those who make it outside—a stunning reminder of the places we hope our research will protect from future eruptions.</p>
<p>We’ll be taking short breaks as we go to appreciate the beauty around us and the excitement of being the first to see new pieces of geologic history, and if you see us from the shore float out some fruit—the bananas are already gone!</p>
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<item>
<title>In Search of Earth’s Secrets on Santorini</title>
<link>https://joidesresolution.org/in-search-of-earths-secrets-on-santorini/?utm_source=rss&utm_medium=rss&utm_campaign=in-search-of-earths-secrets-on-santorini</link>
<comments>https://joidesresolution.org/in-search-of-earths-secrets-on-santorini/#respond</comments>
<dc:creator><![CDATA[Sara Whitlock]]></dc:creator>
<pubDate>Fri, 14 Oct 2022 18:20:36 +0000</pubDate>
<category><![CDATA[Education]]></category>
<category><![CDATA[Scientific Outreach]]></category>
<category><![CDATA[Volcanoes]]></category>
<category><![CDATA[Exhibition]]></category>
<category><![CDATA[EXP398]]></category>
<category><![CDATA[outreach]]></category>
<category><![CDATA[Santorini]]></category>
<category><![CDATA[Science-in-search-of-earths-secrets]]></category>
<guid isPermaLink="false">https://joidesresolution.org/?p=39126</guid>
<description><![CDATA[Next week residents and tourists on the Greek island of Santorini will be invited to explore an exciting interactive geologic... <div class="read-more"><a class="excerpt-read-more" href="https://joidesresolution.org/in-search-of-earths-secrets-on-santorini/" title="Continue reading In Search of Earth’s Secrets on Santorini">Read more<i class="fa fa-angle-right"></i></a></div>]]></description>
<content:encoded><![CDATA[<p>Next week residents and tourists on the Greek island of Santorini will be invited to explore an exciting interactive geologic exhibit about scientific ocean drilling. The International Ocean Discovery Program’s (IODP) traveling exhibit ‘In Search of Earth’s Secrets’ will be in residence at the Bellonio Cultural Center in the town of Fira from October 16-23. The exhibit is expected to host more than 2,000 school children in the mornings, followed by afternoons open to the general public.</p>
<p>The exhibit draws people into a world of marine geologic discovery, featuring video games, a slideshow, microfossils under a microscope, a 3D-printed model of Santorini, a huge floor map of the world, and a miniature inflatable version of the ocean drilling vessel JOIDES Resolution. Visitors can delve deep into the science of ocean drilling and how rock and sediment cores retrieved from the seafloor have helped us solve many of Earth’s biggest geologic mysteries. With activities such as bingo and a sticker passport, the exhibit is fun and educational for kids as well as adults.</p>
<p>The exhibit will set the stage for IODP Expedition 398, which will be scientifically drilling off the coast of Santorini in December, January, and February. This will include a week spent superficial drilling inside the caldera, well in sight of land. The expedition is the culmination of several years of discussion, planning, and preparation by scientists from around the world. More than 30 scientists from 9 countries will be sailing on the ship during the 2-month expedition. The sediment cores retrieved during the expedition will provide a treasure trove of material for further scientific investigation into how and why volcanoes erupt in this region, potentially impacting millions of residents and visitors every year.</p>
<p>Expedition 398 will be setting sail on December 11, 2022. Get ready to follow us on social media and experience the excitement of ocean drilling and marine science from your own home!</p>
<p>Follow us on</p>
<ul>
<li>Twitter: @TheJR</li>
<li>Facebook: https://www.facebook.com/joidesresolution/</li>
<li>Instagram: @joides_resolution</li>
</ul>
<p><strong>Learn More</strong></p>
<ul>
<li>Check out the Expedition 398 <a href="https://joidesresolution.org/expedition/hellenic-arc-volcanic-field/">webpage </a></li>
<li>Read about the <a href="http://publications.iodp.org/scientific_prospectus/398/">scientific plan</a> for the expedition</li>
<li>Learn more about <a href="https://www.iodp.org/about-iodp/history">IODP</a></li>
<li>Learn more about the <a href="https://joidesresolution.org/">JOIDES Resolution</a></li>
</ul>
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<title>The ‘hole’ story about vesicular basalt</title>
<link>https://joidesresolution.org/vesicular-basalt/?utm_source=rss&utm_medium=rss&utm_campaign=vesicular-basalt</link>
<comments>https://joidesresolution.org/vesicular-basalt/#respond</comments>
<dc:creator><![CDATA[Maya Pincus]]></dc:creator>
<pubDate>Sun, 09 Oct 2022 10:58:46 +0000</pubDate>
<category><![CDATA[Education]]></category>
<category><![CDATA[Expeditions]]></category>
<category><![CDATA[Volcanoes]]></category>
<category><![CDATA[basalt]]></category>
<category><![CDATA[EXP391]]></category>
<category><![CDATA[EXP397T]]></category>
<category><![CDATA[hotspot]]></category>
<category><![CDATA[lava]]></category>
<category><![CDATA[volcanoes]]></category>
<guid isPermaLink="false">https://joidesresolution.org/?p=39089</guid>
<description><![CDATA[Whether you know it or not, your life is full of igneous rocks. Maybe it was an obsidian arrowhead in... <div class="read-more"><a class="excerpt-read-more" href="https://joidesresolution.org/vesicular-basalt/" title="Continue reading The ‘hole’ story about vesicular basalt">Read more<i class="fa fa-angle-right"></i></a></div>]]></description>
<content:encoded><![CDATA[<figure id="attachment_39090" aria-describedby="caption-attachment-39090" style="width: 339px" class="wp-caption alignright"><img fetchpriority="high" decoding="async" class="wp-image-39090 " src="https://joidesresolution.org/wp-content/uploads/2022/10/depositphotos_203579150-stock-photo-dutch-river-landscape-view-bridge-300x200.webp" alt="Scene showing a river on the left with a bridge in the background, with large blocks of dark grey rocks alongside the river in the middle of the image." width="339" height="226" srcset="https://joidesresolution.org/wp-content/uploads/2022/10/depositphotos_203579150-stock-photo-dutch-river-landscape-view-bridge-300x200.webp 300w, https://joidesresolution.org/wp-content/uploads/2022/10/depositphotos_203579150-stock-photo-dutch-river-landscape-view-bridge.webp 600w" sizes="(max-width: 339px) 100vw, 339px" /><figcaption id="caption-attachment-39090" class="wp-caption-text">Blocks of basalt alongside a river. (Shutterstock)</figcaption></figure>
<p class="p1">Whether you know it or not, your life is full of igneous rocks. Maybe it was an obsidian arrowhead in a museum (or if you were <i>really</i> lucky, in your backyard). Maybe it was the basalt used as a construction material on a building, outdoor staircase, or alongside a river. Maybe it was the pumice you bought at the pharmacy to buff the dead skin off your feet in the shower. If you really think about it, igneous rocks are everywhere.</p>
<p class="p1">Want to know where there are REALLY a lot of igneous rocks? Underneath the ocean. Oceanic crust forms at mid-ocean ridges, where plate tectonics are in the act of tearing Earth’s surface apart. As tectonic plates rift away from each other, material from the mantle, made molten by the sudden reduction in pressure, bubbles up to fill the void and crystallizes to form new crust. Over time these rocks get covered in marine sediments, composed of the finest mud and hundreds of meters of nannofossil ooze, forming the ocean floor as we know it today.</p>
<figure id="attachment_39091" aria-describedby="caption-attachment-39091" style="width: 300px" class="wp-caption alignleft"><img decoding="async" class="wp-image-39091 size-medium" src="https://joidesresolution.org/wp-content/uploads/2022/10/pillowlava.v2-300x225.jpg" alt="Pile of globular dark rocks under water with a small amount of red lava visible in the bottom right corner." width="300" height="225" srcset="https://joidesresolution.org/wp-content/uploads/2022/10/pillowlava.v2-300x225.jpg 300w, https://joidesresolution.org/wp-content/uploads/2022/10/pillowlava.v2.jpg 324w" sizes="(max-width: 300px) 100vw, 300px" /><figcaption id="caption-attachment-39091" class="wp-caption-text">Basaltic lavas forming along the Juan de Fuca mid-ocean ridge. (SERC)</figcaption></figure>
<p class="p1">Extinct volcanoes like those of the Walvis Ridge are also made of igneous rocks. The sister expeditions EXP391 and EXP397T sailed over a thousand kilometers from Cape Town to drill hundreds of meters below the ocean floor to attempt to retrieve these igneous rocks. The basaltic lavas that flowed out of these volcanoes 60 to 130 million years ago hold the clues that will help us understand why the Walvis Ridge is just so weird.</p>
<p class="p1">For the majority of Earth’s history, misconceptions about the nature of our Earth have abounded. If we drill into the side of a volcano, will that release all the magma stored inside and lead to a massive volcanic eruption? If we drill into the Earth, will the whole planet deflate, or even pop like a balloon?</p>
<p class="p1">Fortunately [scientifically], no.</p>
<p class="p1">More negligible than a mosquito’s proboscis on the flank of an elephant, the drill of the <i>JOIDES Resolution</i> is about 25 centimeters wide, drilling into volcanoes that are 25 <i>kilometers</i> across. The volcanoes we are drilling into are far from active. In some cases, they have been extinct for over 100 million years.</p>
<p class="p1">The cores that we recover from the slopes of these dead volcanoes are a mere 6 cm across. How is it possible that we can learn <i>anything</i> from a tube of rock that narrow? It’s amazing what stories we can tell when that tube is 100 m long.</p>
<p class="p1">You can think of a core as a time machine, with a little less drama than the industry-standard blinking lights and spooky humming. The principles of stratigraphy tell us that (in an area that has not been deformed by folding), as we go deeper, the rocks we encounter get older. The ooze that is characteristic of the first several cores is the youngest material we collect, the more lithified sediments that get pulled up next, from deeper in the hole, are older, and finally the basaltic basement rock that we eventually reach is the oldest. The higher the core number, the longer ago we are looking into Earth’s past.<span class="Apple-converted-space"> </span></p>
<p> </p>
<p class="p1"><b>Anatomy of a volcano</b></p>
<p class="p1">What makes a volcano <i>a volcano</i> is the magma chamber inside. This is essentially a pool of molten rock that has risen towards the surface of Earth due to its high temperatures. Hot materials tend to be less dense, and therefore more buoyant. The characteristics of the magma are dependent on many factors, and can vary widely. Some magmas are rich in elements like iron and magnesium, while others tend to have more silicon and aluminum. Some magmas are viscous while others are liquidy-smooth. Some are pure molten rock, while others contain dissolved gases such as water vapor, carbon dioxide, and sulfur dioxide.</p>
<figure id="attachment_39092" aria-describedby="caption-attachment-39092" style="width: 178px" class="wp-caption alignright"><img decoding="async" class=" wp-image-39092" src="https://joidesresolution.org/wp-content/uploads/2022/10/001397056-300x300.jpg" alt="An unopened bottle of Coca-Cola with red cap, red label, and white writing." width="178" height="178" srcset="https://joidesresolution.org/wp-content/uploads/2022/10/001397056-300x300.jpg 300w, https://joidesresolution.org/wp-content/uploads/2022/10/001397056-150x150.jpg 150w, https://joidesresolution.org/wp-content/uploads/2022/10/001397056-768x768.jpg 768w, https://joidesresolution.org/wp-content/uploads/2022/10/001397056.jpg 800w" sizes="(max-width: 178px) 100vw, 178px" /><figcaption id="caption-attachment-39092" class="wp-caption-text">In an unopened bottle of soda, no bubbles are visible.</figcaption></figure>
<p class="p1">These gassy magmas are the ones we will focus on for the rest of this post. The next time you’re near an unopened bottle of soda, take a moment to make some observations. Can you see any bubbles? If so, are there a lot, or very few?</p>
<p class="p1">The reason you <i>can’t</i> see a lot of bubbles is that the contents of that bottle are under some serious pressure. You can verify this by giving the bottle a squeeze. It feels so hard because of the high pressure inside. It is this high pressure that allows the carbon dioxide to dissolve into the liquid of the soda, essentially disappearing. In other words, as long as that bottle remains unopened, the liquid and gas are perfectly blended into a homogeneous mmixture, forced together under pressure.<span class="Apple-converted-space"> </span></p>
<p class="p1">But what happens the moment you open the bottle? At the sudden release of pressure, the carbon dioxide is no longer forced to mix with the liquid, and instead makes its way out in the form of thousands of little bubbles. If you disturbed the bottle prior to opening it, the small act of relieving pressure may even result in an explosion.</p>
<p class="p1">Let’s return from this analogy to back to volcanoes. As long as the magma stays inside the volcano, the pressure of being underground keeps those gases dissolved. But as soon as the volcano begins to erupt, the dissolved gases are free to expand and make their way out of the melt.</p>
<p class="p1">In the case of the Walvis Ridge volcanoes, the rock that results from this process is what’s known as a vesicular basalt. “Vesicular” refers to the gas bubbles, or vesicles, that were trapped and frozen in place as the rock crystallized, and “basalt” means that the lava was rich in iron and magnesium, indicating an oceanic crust or mantle source.</p>
<figure id="attachment_39093" aria-describedby="caption-attachment-39093" style="width: 317px" class="wp-caption alignright"><img loading="lazy" decoding="async" class="wp-image-39093 " src="https://joidesresolution.org/wp-content/uploads/2022/10/IMG_3902-225x300.jpeg" alt="Picture of a core half showing a dark gray basalt with a black chilled rim at the top, with several empty vesicles and pistachio-green in-filled pipe vesicles." width="317" height="423" srcset="https://joidesresolution.org/wp-content/uploads/2022/10/IMG_3902-225x300.jpeg 225w, https://joidesresolution.org/wp-content/uploads/2022/10/IMG_3902-768x1024.jpeg 768w, https://joidesresolution.org/wp-content/uploads/2022/10/IMG_3902-1152x1536.jpeg 1152w, https://joidesresolution.org/wp-content/uploads/2022/10/IMG_3902-1536x2048.jpeg 1536w, https://joidesresolution.org/wp-content/uploads/2022/10/IMG_3902-scaled.jpeg 1920w" sizes="auto, (max-width: 317px) 100vw, 317px" /><figcaption id="caption-attachment-39093" class="wp-caption-text">Vesicles frozen into the basalt on their way to the surface. (Maya Pincus)</figcaption></figure>
<p class="p1">Just like in a glass of soda, as the lava hardens and crystallizes into solid rocks, the gas bubbles try to make their way up and out. We can actually see evidence of this in basalt cores collected during Expedition 391. In the picture to the right, you can see a fragment of what is called a pillow basalt, similar to the image above from the mid-ocean ridge. The black edge towards the top of the picture is the outer shell of the lava pillow, and you can see several vesicles (some filled in with a green secondary mineral) in the process of making their way to the top of the rock.</p>
<p class="p1">Just like with soda, this process makes sense. Gas bubbles are much less dense than liquid (whether it is liquid cola or liquid rock) so they float to the surface.</p>
<p class="p1">So then what does it mean if we find vesicles <i>in the middle</i> of a core? During Expedition 397T, we recovered tens of meters of basalt. Unlike the rocks we recovered during Expedition 391, there is very little change in the basalt throughout all the cores, indicating a massive lava flow. But instead of finding vesicles near the boundaries between flows, we are observing them right in the middle of a crystallized basalt.</p>
<p class="p1">How did those bubbles get there?</p>
<figure id="attachment_39094" aria-describedby="caption-attachment-39094" style="width: 563px" class="wp-caption aligncenter"><img loading="lazy" decoding="async" class=" wp-image-39094" src="https://joidesresolution.org/wp-content/uploads/2022/10/IMG_3437-300x225.jpeg" alt="Several rows of split basaltic core. The sections in the middle are vesicular." width="563" height="422" srcset="https://joidesresolution.org/wp-content/uploads/2022/10/IMG_3437-300x225.jpeg 300w, https://joidesresolution.org/wp-content/uploads/2022/10/IMG_3437-1024x768.jpeg 1024w, https://joidesresolution.org/wp-content/uploads/2022/10/IMG_3437-768x576.jpeg 768w, https://joidesresolution.org/wp-content/uploads/2022/10/IMG_3437-1536x1152.jpeg 1536w, https://joidesresolution.org/wp-content/uploads/2022/10/IMG_3437-2048x1536.jpeg 2048w" sizes="auto, (max-width: 563px) 100vw, 563px" /><figcaption id="caption-attachment-39094" class="wp-caption-text">These basalts have vesicles in the middle instead of near the surface. (Maya Pincus)</figcaption></figure>
<p> </p>
<p class="p1">Expedition 397T scientists have been doing the detective work, observing and describing the cores centimeter by centimeter to try to figure it out. By comparing their analyses of these cores to known volcanic processes they are now able to tell the ‘hole’ story.</p>
<p> </p>
<p class="p1"><b>Eruptions over time</b></p>
<p class="p1">The case of the core-bound bubble can be explained by what’s known as “lava inflation events” that occurred over time. As evidenced by the recent volcanic eruptions in Iceland, volcanic eruptions can continue over a period of several months. Though this is minimal in terms of geologic time, it is significant enough to lead to visible patterns in the rocks that form from it.</p>
<p class="p1">When a volcano initially erupts, it deposits a flow of lava along its flanks. If left uninterrupted, this lava will eventually cool and turn into rock. If there was gas dissolved in the melt, vesicles should be found near the surface of the rock, trapped on their way to the atmosphere.</p>
<p class="p1">If the volcano continues to erupt, some of the new lava might spill out on top of the previous flow. However, some of that lava might actually be injected underneath the previous flow.<span class="Apple-converted-space"> </span></p>
<p class="p1">This process is referred to as lava inflation because over time the new lava “inflates” the preexisting igneous rock. Igneous petrologist Dr. Wendy Nelson likens it to inflating a bike tire with air, or a donut with filling.</p>
<figure id="attachment_39098" aria-describedby="caption-attachment-39098" style="width: 273px" class="wp-caption alignleft"><img loading="lazy" decoding="async" class=" wp-image-39098" src="https://joidesresolution.org/wp-content/uploads/2022/10/IMG_3705-225x300.jpeg" alt="A 10cm long piece of dark gray basalt. Vesicles are present in the top half, but not the bottom half." width="273" height="364" srcset="https://joidesresolution.org/wp-content/uploads/2022/10/IMG_3705-225x300.jpeg 225w, https://joidesresolution.org/wp-content/uploads/2022/10/IMG_3705-768x1024.jpeg 768w, https://joidesresolution.org/wp-content/uploads/2022/10/IMG_3705-1152x1536.jpeg 1152w, https://joidesresolution.org/wp-content/uploads/2022/10/IMG_3705-1536x2048.jpeg 1536w, https://joidesresolution.org/wp-content/uploads/2022/10/IMG_3705-scaled.jpeg 1920w" sizes="auto, (max-width: 273px) 100vw, 273px" /><figcaption id="caption-attachment-39098" class="wp-caption-text">Sometimes it is very obvious which way is “up” just from the vesicles.</figcaption></figure>
<p class="p1">In the case of EXP397T basalts, the lava inflation event must have occurred soon enough after the original eruption that the lava was still warm, but solid enough that gas bubbles got trapped between layers and were unable to rise all the way to the surface. We know that the lava was still warm because we don’t see any quench boundaries or chill margins, which are textures that occur when hot lava interacts with a cold surrounding environment. However, the lava must have been solidified just enough, while still warm, that it created a boundary solid enough to prevent gas bubbles to continue their upward journey.</p>
<p class="p1">When people from outside the scientific drilling community look at a core, they see a pile of tubular rocks. But when our scientists look at cores what they see is a story over time. Each centimeter of core is one more page in the book of Earth’s history.</p>
<p> </p>
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<title>On Ocean Drilling and Expectations</title>
<link>https://joidesresolution.org/on-ocean-drilling-and-expectations/?utm_source=rss&utm_medium=rss&utm_campaign=on-ocean-drilling-and-expectations</link>
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<dc:creator><![CDATA[Maya Pincus]]></dc:creator>
<pubDate>Sat, 24 Sep 2022 16:10:14 +0000</pubDate>
<category><![CDATA[Drilling]]></category>
<category><![CDATA[Education]]></category>
<category><![CDATA[Physcial Properties]]></category>
<category><![CDATA[Technology]]></category>
<category><![CDATA[Volcanoes]]></category>
<category><![CDATA[drilling]]></category>
<category><![CDATA[EXP397T]]></category>
<category><![CDATA[seismic survey]]></category>
<guid isPermaLink="false">https://joidesresolution.org/?p=39048</guid>
<description><![CDATA[This post was written with contributions from Expedition 397T Co-Chief Scientist Dr. Will Sager.   At this point I’ve led... <div class="read-more"><a class="excerpt-read-more" href="https://joidesresolution.org/on-ocean-drilling-and-expectations/" title="Continue reading On Ocean Drilling and Expectations">Read more<i class="fa fa-angle-right"></i></a></div>]]></description>
<content:encoded><![CDATA[<p class="p1"><i>This post was written with contributions from Expedition 397T Co-Chief Scientist Dr. Will Sager.</i></p>
<p> </p>
<p class="p1">At this point I’ve led more than fifty live ship-to-shore broadcasts from the <i>JOIDES Resolution</i>, and a question that students ask time after time is “How do you know where to drill?”</p>
<p class="p1">This is a fun question to answer, because no matter what the audience expected, the scope of planning where to drill for any given expedition goes beyond their wildest expectations. It’s also bitingly relevant now, as core after Expedition 397T core gives us something different from what we were hoping for.</p>
<p> </p>
<h5><strong>WE WANNA ROCK</strong></h5>
<p class="p1">Expedition 397T came to the Walvis Ridge for basalt. The Walvis Ridge is a hotspot track, which means it was formed by the eruptions of volcanoes not at the boundaries between tectonic plates, but due to upwellings of hot, buoyant mantle material. Walvis Ridge is remarkably complex, and unlike any other known hotspot track; for this reason Expedition 391 and the bonus Expedition 397T have been dedicated to understanding its mystery.</p>
<figure id="attachment_39060" aria-describedby="caption-attachment-39060" style="width: 276px" class="wp-caption alignleft"><img loading="lazy" decoding="async" class=" wp-image-39060" src="https://joidesresolution.org/wp-content/uploads/2022/09/IMG_3450-225x300.jpeg" alt="An image of a classic Walvis Ridge basalt core: fine-grained, dark gray, with flecks of white." width="276" height="368" srcset="https://joidesresolution.org/wp-content/uploads/2022/09/IMG_3450-225x300.jpeg 225w, https://joidesresolution.org/wp-content/uploads/2022/09/IMG_3450-768x1024.jpeg 768w, https://joidesresolution.org/wp-content/uploads/2022/09/IMG_3450-1152x1536.jpeg 1152w, https://joidesresolution.org/wp-content/uploads/2022/09/IMG_3450-1536x2048.jpeg 1536w, https://joidesresolution.org/wp-content/uploads/2022/09/IMG_3450-scaled.jpeg 1920w" sizes="auto, (max-width: 276px) 100vw, 276px" /><figcaption id="caption-attachment-39060" class="wp-caption-text">A classic Walvis Ridge basalt.</figcaption></figure>
<p class="p1">Basalt is a fine-grained, mafic igneous rock. Its small crystal size means that it forms on Earth’s crust, rather than inside it (in other words, it erupted out of a volcano), and mafic describes the composition of the rock, indicating an origin in the mantle. Seeking the rocks that came directly out of the Walvis Ridge hotspot volcanoes is crucial to achieving the scientific objectives of the expedition.</p>
<p class="p1">First of all, it is geochemically important that we are studying these lava flows. Given the complexity of the Walvis Ridge, we are trying to figure out what exactly is going on inside Earth that led to the formation of such an unusual ridge. Geochemical analyses of the composition of the basalt at different locations along the ridge will tell us how many distinct mantle sources were involved in the volcanism, and if there was any mixing between sources.<span class="Apple-converted-space"> </span></p>
<p class="p1">Rocks in the Walvis Ridge may also hold the key to demonstrating that Earth’s experienced a shift relative to its axis of rotation at the time of their formation. Known as true polar wander, this process is highly contentious among geoscientists. In order to test that true polar wander occurred, we need to analyze the magnetic field preserved in the rocks at the time of their formation, and basalt that formed <em>i</em><em>n situ</em> can be remarkably good at recording an ancient magnetic field.</p>
<p> </p>
<h5><strong>MAKING WAVES</strong></h5>
<figure id="attachment_39053" aria-describedby="caption-attachment-39053" style="width: 386px" class="wp-caption alignright"><img loading="lazy" decoding="async" class=" wp-image-39053" src="https://joidesresolution.org/wp-content/uploads/2022/09/Screen-Shot-2022-09-24-at-10.44.39-AM-300x196.png" alt="Screenshot of Google Maps showing the Walvis Ridge." width="386" height="252" srcset="https://joidesresolution.org/wp-content/uploads/2022/09/Screen-Shot-2022-09-24-at-10.44.39-AM-300x196.png 300w, https://joidesresolution.org/wp-content/uploads/2022/09/Screen-Shot-2022-09-24-at-10.44.39-AM-1024x670.png 1024w, https://joidesresolution.org/wp-content/uploads/2022/09/Screen-Shot-2022-09-24-at-10.44.39-AM-768x502.png 768w, https://joidesresolution.org/wp-content/uploads/2022/09/Screen-Shot-2022-09-24-at-10.44.39-AM-1536x1005.png 1536w, https://joidesresolution.org/wp-content/uploads/2022/09/Screen-Shot-2022-09-24-at-10.44.39-AM.png 1908w" sizes="auto, (max-width: 386px) 100vw, 386px" /><figcaption id="caption-attachment-39053" class="wp-caption-text">Bathymetric image of the Walvis Ridge. From Google Maps.</figcaption></figure>
<p class="p1">So, we know what we want. But how do we make sure to go where we can get it? The first thing to consider is bathymetry. Though a complicated word, bathymetry simply refers to the shape of the ocean floor. If you go to Google Maps and choose the satellite layer, you can see a pretty decent bathymetric map, showing submarine peaks and valleys just as, if not more, complex than Earth’s continents. When you look at the bathymetry of Walvis Ridge, you can see why scientists are so fascinated by it. To the northeast is the Valdivia Bank, a somewhat squiggly broad underwater plateau. To the southwest is the “trident” the area where the hotspot track branches into three distinct chains. We can use bathymetry to identify the Walvis Ridge volcanoes that we want to drill into.</p>
<p class="p1">However, bathymetry only tells us what the seafloor looks like. If we’re going to drill down, we also need to know what’s <i>under</i> the seafloor.</p>
<p class="p1">How is it possible to know what lies beneath the ocean floor without drilling into it first? Just like doctors send x-ray waves into our bodies to see where we’ve broken a bone, scientists send seismic waves to see what the ground is made of underneath the surface.</p>
<p class="p1">Scientists have known that earthquakes send waves through the planet since before the advent of modern religion. As technology advanced and seismometers were developed, scientists realized that seismic waves travel differently through different materials. This helped us determine that Earth’s interior is differentiated into layers, and it is the same principle that allows us to interpret unseen geology at a more local level.<span class="Apple-converted-space"> </span></p>
<figure id="attachment_39062" aria-describedby="caption-attachment-39062" style="width: 323px" class="wp-caption alignleft"><img loading="lazy" decoding="async" class=" wp-image-39062" src="https://joidesresolution.org/wp-content/uploads/2022/09/istockphoto-1336616471-612x612-1-300x225.jpg" alt="A cartoon showing a ship on the ocean sending acoustic waves into the water. The waves penetrate layers of sediments then bounce off a rock layer. The reflected waves are recorded by monitors behind the ship." width="323" height="242" srcset="https://joidesresolution.org/wp-content/uploads/2022/09/istockphoto-1336616471-612x612-1-300x225.jpg 300w, https://joidesresolution.org/wp-content/uploads/2022/09/istockphoto-1336616471-612x612-1.jpg 612w" sizes="auto, (max-width: 323px) 100vw, 323px" /><figcaption id="caption-attachment-39062" class="wp-caption-text">A ship sends acoustic waves toward the seafloor and measures the speed at which they bounce back to infer stratigraphy. From iStock.</figcaption></figure>
<p class="p1">Here’s how it works: a scientist will go out into the ocean on a boat and use a machine to send low-frequency acoustic waves to the bottom of the ocean. Some of those waves will bounce back when they hit the ocean floor, but some will penetrate into the layers of sediment and rock that comprise the seafloor before being reflected back to the surface.<span class="Apple-converted-space"> </span></p>
<p class="p1">As the seismic waves make their way back to the ocean surface where they are recorded by another instrument, there are two ways that they can help us interpret geology: seismic velocities and seismic reflectors. Each material has its own seismic velocity – the speed at which seismic waves can travel through it. Thanks to tens of years and hundreds of experiments, we know pretty accurately what material waves are traveling through based on their speed. For example, basalt is much denser than sediment, so seismic waves travel more quickly through it.</p>
<p class="p1">Another way that seismic waves help us interpret geology is because of something called reflectors. Each time a seismic wave travels through a new material, the velocity changes, but an amount of the wave also is reflected by the new layer and sent back to the recording instrument.<span class="Apple-converted-space"> </span></p>
<p class="p1">When the data are processed by a computer program, the result is an image like the one below. By interpreting the different seismic velocities measured, and the locations of different reflectors, it is possible to infer where the ocean water becomes sediment, and where the sediment transitions into igneous basement rock.</p>
<figure id="attachment_39054" aria-describedby="caption-attachment-39054" style="width: 664px" class="wp-caption aligncenter"><img loading="lazy" decoding="async" class=" wp-image-39054" src="https://joidesresolution.org/wp-content/uploads/2022/09/Screen-Shot-2022-09-24-at-10.51.47-AM-300x268.png" alt="A two-part image from the EXP397T Scientific Prospectus showing an uninterpreted seismic profile on top (alternating squiggly red an blue lines sloping down toward the right side) and interpreted to the bottom (the top of the seismic profile has been coded yellow to show inferred pelagic sediments and purple on the bottom to show inferred basement rock)." width="664" height="593" srcset="https://joidesresolution.org/wp-content/uploads/2022/09/Screen-Shot-2022-09-24-at-10.51.47-AM-300x268.png 300w, https://joidesresolution.org/wp-content/uploads/2022/09/Screen-Shot-2022-09-24-at-10.51.47-AM-1024x916.png 1024w, https://joidesresolution.org/wp-content/uploads/2022/09/Screen-Shot-2022-09-24-at-10.51.47-AM-768x687.png 768w, https://joidesresolution.org/wp-content/uploads/2022/09/Screen-Shot-2022-09-24-at-10.51.47-AM.png 1066w" sizes="auto, (max-width: 664px) 100vw, 664px" /><figcaption id="caption-attachment-39054" class="wp-caption-text">Seismic line crossing proposed Sites GT-4A and GT-6A. Top: uninterpreted data. Bottom: interpretation. Columns = approximate sections to be cored, horizontal line in column = approximate depth at which coring will begin. CMP = common midpoint, VE = vertical exaggeration. SF = seafloor, B = acoustic basement. From EXP397T Scientific Prospectus.</figcaption></figure>
<p> </p>
<h5><strong>SEEING IS BELIEVING</strong></h5>
<p class="p1">The science sounds bulletproof, right?</p>
<p class="p1">Wrong. Unfortunately.</p>
<p class="p1">Drilling into site GT-6A was an exercise in unfulfilled expectations. Seismic profiles indicated that we should hit igneous basement rock approximately 165 m below the seafloor. We planned to “wash” down to 145 m<span style="font-weight: 400;">—</span>drill without collecting cores<span style="font-weight: 400;">—</span>so that we could recover about 20 m of sedimentary rock before we hit the basalt we were aiming for. These two cores of sedimentary rock would be useful for telling us more about the undersea environment we were working in, and would very likely contain fossils that would allow us to approximate a minimum age for the lava flow below them.</p>
<p class="p1">About 170 m below the seafloor, the drillers sensed a change. All of a sudden there was a drop in torque and the rate of drilling drastically decreased. This kind of change typically indicates the transition from drilling through relatively soft sedimentary rock to something much harder. In other words, every indication told us we reached basalt.</p>
<p class="p1">But the cores we recovered were not that. Instead of uniform dark-grey igneous rock, our split cores revealed a kaleidoscope of green, white, brown, red, and black fragments cemented together. What we thought was going to be a standard run-of-the-mill igneous rock was instead a frenetic jumble of volcaniclastics lithified into a breccia.<span class="Apple-converted-space"> </span></p>
<p class="p1"><img loading="lazy" decoding="async" class=" wp-image-39057 aligncenter" src="https://joidesresolution.org/wp-content/uploads/2022/09/Screen-Shot-2022-09-24-at-2.25.51-PM-300x159.png" alt="Left: Basalt cores from Expedition 391 labeled "WHAT WE WANTED" Right: Breccia from Expedition 397T labeled "WHAT WE GOT"" width="579" height="307" srcset="https://joidesresolution.org/wp-content/uploads/2022/09/Screen-Shot-2022-09-24-at-2.25.51-PM-300x159.png 300w, https://joidesresolution.org/wp-content/uploads/2022/09/Screen-Shot-2022-09-24-at-2.25.51-PM-1024x543.png 1024w, https://joidesresolution.org/wp-content/uploads/2022/09/Screen-Shot-2022-09-24-at-2.25.51-PM-768x407.png 768w, https://joidesresolution.org/wp-content/uploads/2022/09/Screen-Shot-2022-09-24-at-2.25.51-PM-1536x814.png 1536w, https://joidesresolution.org/wp-content/uploads/2022/09/Screen-Shot-2022-09-24-at-2.25.51-PM-2048x1086.png 2048w" sizes="auto, (max-width: 579px) 100vw, 579px" /></p>
<p> </p>
<p class="p1">This was not so unusual; even in Expedition 391 we found layers like this above the basalt we sought. Rocks like these tend to form when volcanoes erupt pyroclastically in shallow water. If we kept drilling, we would soon reach what we came for.</p>
<p>Right?</p>
<p>Wrong. Unfortunately.</p>
<p>Core after core at our first site yielded that breccia that was so beautiful, but so irrelevant to our goals. The fragments of igneous rock preserved in the breccia were too altered to preserve the geochemical information we need, and without an orientation they could do little to offer an answer to the question of true polar wander.</p>
<p>So what could we do? Our coring time for this expedition is very limited, given that we need to transit all the way to Lisbon. Eventually, our co-chief and expedition project manager made the decision to leave the site and try to find basalt somewhere else.</p>
<p>After the success we had finding basalt during Expedition 391, we thought it would be easy a second time around. But as EPM Peter reminds us, “We just have no idea what’s down there. We know the surface of Mars better than we know the seafloor.”</p>
<p>And despite the disappointment that Co-Chief Will felt, he makes a pretty good point: “If we knew what we were going to find, we probably wouldn’t need to drill into it in the first place.”</p>
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<title>The Transect (Video)</title>
<link>https://joidesresolution.org/the-transect-video/?utm_source=rss&utm_medium=rss&utm_campaign=the-transect-video</link>
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<dc:creator><![CDATA[MGarnsworthy]]></dc:creator>
<pubDate>Wed, 04 May 2022 06:25:50 +0000</pubDate>
<category><![CDATA[Climate Change]]></category>
<category><![CDATA[Education]]></category>
<category><![CDATA[Geochemistry]]></category>
<category><![CDATA[Geological time]]></category>
<category><![CDATA[History of Earth]]></category>
<category><![CDATA[Microbes]]></category>
<category><![CDATA[petrology]]></category>
<category><![CDATA[Plate Tectonics]]></category>
<category><![CDATA[Volcanoes]]></category>
<category><![CDATA[drilling]]></category>
<category><![CDATA[EXP390]]></category>
<category><![CDATA[Exp393]]></category>
<category><![CDATA[Mid-Atlantic Ridge]]></category>
<category><![CDATA[seafloor spreading]]></category>
<guid isPermaLink="false">https://joidesresolution.org/?p=38257</guid>
<description><![CDATA[Why are Expeditions 390 & 393 on a transect of the South Atlantic Ocean? Find out in this sixth video... <div class="read-more"><a class="excerpt-read-more" href="https://joidesresolution.org/the-transect-video/" title="Continue reading The Transect (Video)">Read more<i class="fa fa-angle-right"></i></a></div>]]></description>
<content:encoded><![CDATA[<p>Why are Expeditions 390 & 393 on a transect of the South Atlantic Ocean?</p>
<p>Find out in this sixth video in the Exp 390 Story Series!</p>
<div style="width: 1200px;" class="wp-video"><!--[if lt IE 9]><script>document.createElement('video');</script><![endif]-->
<video class="wp-video-shortcode" id="video-38257-1" width="1200" height="675" preload="metadata" controls="controls"><source type="video/mp4" src="https://joidesresolution.org/wp-content/uploads/2022/05/Video-6-The-Transect_1.mp4?_=1" /><a href="https://joidesresolution.org/wp-content/uploads/2022/05/Video-6-The-Transect_1.mp4">https://joidesresolution.org/wp-content/uploads/2022/05/Video-6-The-Transect_1.mp4</a></video></div>
<p> </p>
<p> </p>
]]></content:encoded>
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<title>Transit – 390C Core Description Part 1 (Video)</title>
<link>https://joidesresolution.org/transit-390c-core-description-part-1-video/?utm_source=rss&utm_medium=rss&utm_campaign=transit-390c-core-description-part-1-video</link>
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<dc:creator><![CDATA[MGarnsworthy]]></dc:creator>
<pubDate>Tue, 19 Apr 2022 08:26:10 +0000</pubDate>
<category><![CDATA[Drilling]]></category>
<category><![CDATA[Geological time]]></category>
<category><![CDATA[History of Earth]]></category>
<category><![CDATA[Microfossils]]></category>
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<category><![CDATA[#Exp390C]]></category>
<category><![CDATA[EXP390]]></category>
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<description><![CDATA[On Expedition 390, we’re still transiting to our first drill site. It’s a long transit of 8 days. Normally, we... <div class="read-more"><a class="excerpt-read-more" href="https://joidesresolution.org/transit-390c-core-description-part-1-video/" title="Continue reading Transit – 390C Core Description Part 1 (Video)">Read more<i class="fa fa-angle-right"></i></a></div>]]></description>
<content:encoded><![CDATA[<p>On Expedition 390, we’re still transiting to our first drill site. It’s a long transit of 8 days. Normally, we would not be working on sediment cores until we reach our site and begin drilling.</p>
<p>However, our scientists continue their sediment core descriptions of material drilled from our sites on preliminary expedition 390C. This video explains more about the core description process.</p>
<div style="width: 1200px;" class="wp-video"><video class="wp-video-shortcode" id="video-38163-2" width="1200" height="675" preload="metadata" controls="controls"><source type="video/mp4" src="https://joidesresolution.org/wp-content/uploads/2022/04/Core-Description-Part-1-SMALL_1.mp4?_=2" /><a href="https://joidesresolution.org/wp-content/uploads/2022/04/Core-Description-Part-1-SMALL_1.mp4">https://joidesresolution.org/wp-content/uploads/2022/04/Core-Description-Part-1-SMALL_1.mp4</a></video></div>
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<title>Meet the Exp391 Lab Teams!</title>
<link>https://joidesresolution.org/meet-the-exp391-lab-teams/?utm_source=rss&utm_medium=rss&utm_campaign=meet-the-exp391-lab-teams</link>
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<dc:creator><![CDATA[Maya Pincus]]></dc:creator>
<pubDate>Thu, 06 Jan 2022 18:11:16 +0000</pubDate>
<category><![CDATA[Drilling]]></category>
<category><![CDATA[Expeditions]]></category>
<category><![CDATA[Geochemistry]]></category>
<category><![CDATA[Microfossils]]></category>
<category><![CDATA[Paleomagnetism]]></category>
<category><![CDATA[Physcial Properties]]></category>
<category><![CDATA[Plate Tectonics]]></category>
<category><![CDATA[Scientist Profiles]]></category>
<category><![CDATA[Sedimentology]]></category>
<category><![CDATA[STEM Careers]]></category>
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<category><![CDATA[core flow]]></category>
<category><![CDATA[EXP391]]></category>
<category><![CDATA[meet the scientists]]></category>
<guid isPermaLink="false">https://joidesresolution.org/?p=37630</guid>
<description><![CDATA[Now that we have core on deck, life on the JOIDES Resolution is wildly different. While quarantined in port, you... <div class="read-more"><a class="excerpt-read-more" href="https://joidesresolution.org/meet-the-exp391-lab-teams/" title="Continue reading Meet the Exp391 Lab Teams!">Read more<i class="fa fa-angle-right"></i></a></div>]]></description>
<content:encoded><![CDATA[<p class="p1">Now that we have core on deck, life on the <i>JOIDES Resolution</i> is wildly different. While quarantined in port, you could find us wandering around aimlessly, playing cards, eating too many cookies, and counting down the minutes to our next COVID test (because there was NOTHING else to look forward to). We lived in a crescendo of alternating despair and ennui.</p>
<p class="p1">Now that we have core on deck, life on the <i>JOIDES Resolution</i> is wildly different. We no longer bump into each other as we pace the hallways, wondering if there is a purpose to us existing on the boat, or even on the planet. We found our motivation, our driving force, the reason we said good-bye to our loved ones to live at sea for sixty days.</p>
<p class="p1">NOW.</p>
<p class="p1">WE.</p>
<p class="p1">HAVE.</p>
<p class="p1">CORE.</p>
<p class="p1">We are ready to do what we came here to do.</p>
<p class="p1">What’s so striking about this endeavor is just how unique our samples are. Right now, we are the only humans on the entire planet who have access to these rocks. If it weren’t for ocean drilling, people would have to wait hundreds of millions of years for the rocks to <em>maybe</em> be uplifted from below the sea. In all likelihood, these rocks would be subducted, melted down and recycled, and never ever exposed in a place on Earth’s surface where they could be observed.</p>
<p class="p1">With the power of exclusive access to these one-of-a-kind materials comes great responsibility. Our role while at sea is to prepare these cores in a way that enables not just us, but the entire world, to carry out investigations that will push the bounds of scientific knowledge. The rig floor is not the only part of this ship that is a well-oiled machine. Each of the Expedition 391 scientists has a very specific purpose within the lab to make sure that all the data we need is collected thoroughly, accurately, and as efficiently as possible.</p>
<p class="p1">Read on to meet the <strong>Doers of Science</strong>, the conduits between the ocean floor and the greater scientific world. Presenting… the LAB TEAMS OF EXPEDITION 391.</p>
<figure id="attachment_37631" aria-describedby="caption-attachment-37631" style="width: 338px" class="wp-caption alignright"><img loading="lazy" decoding="async" class="wp-image-37631" src="https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2066-225x300.jpeg" alt="" width="338" height="450" srcset="https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2066-225x300.jpeg 225w, https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2066-768x1024.jpeg 768w, https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2066-1152x1536.jpeg 1152w, https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2066-1536x2048.jpeg 1536w, https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2066-scaled.jpeg 1920w" sizes="auto, (max-width: 338px) 100vw, 338px" /><figcaption id="caption-attachment-37631" class="wp-caption-text">From left to right: Sharmonay, Ethan, Katie</figcaption></figure>
<p> </p>
<p> </p>
<p><em><strong>Physical Properties: </strong>Physical properties and downhole measurements are the very first step to understanding sediment and rock recovered from Walvis Ridge, which means that physical properties scientists get the very first glimpse of the core. Physical properties scientists scan cores in a variety of instruments (much like a cat scan) for data such as density, moisture content, and P-wave velocity. Next, they combine these data with downhole wireline logs to build a framework for understanding all other scientific observations made during Expedition 391. Are physical properties and downhole measurements important? Of cores!</em></p>
<ul class="ul1">
<li class="li1">Sharmonay Fielding (University of Namibia)<span class="Apple-converted-space"> </span></li>
<li class="li1">Dr. Katherine Potter (Utah State University)</li>
<li class="li1">Ethan Petrou (Oxford University)</li>
</ul>
<p> </p>
<figure id="attachment_37642" aria-describedby="caption-attachment-37642" style="width: 143px" class="wp-caption alignleft"><img loading="lazy" decoding="async" class="size-medium wp-image-37642" src="https://joidesresolution.org/wp-content/uploads/2022/01/Simone_Pujatti-143x300.jpeg" alt="" width="143" height="300" srcset="https://joidesresolution.org/wp-content/uploads/2022/01/Simone_Pujatti-143x300.jpeg 143w, https://joidesresolution.org/wp-content/uploads/2022/01/Simone_Pujatti-488x1024.jpeg 488w, https://joidesresolution.org/wp-content/uploads/2022/01/Simone_Pujatti.jpeg 610w" sizes="auto, (max-width: 143px) 100vw, 143px" /><figcaption id="caption-attachment-37642" class="wp-caption-text">Simone Pujatti</figcaption></figure>
<p> </p>
<p> </p>
<p> </p>
<p>FEATURED ONSHORE SCIENTIST: Simone Pujatti (University of Calgary). Simone is actively supporting the efforts of the offshore petrophysics team by writing and reviewing methodology and site reports. Additionally, he will be helping remotely with data management with the successful drilling of each hole.</p>
<p> </p>
<p> </p>
<figure id="attachment_37633" aria-describedby="caption-attachment-37633" style="width: 390px" class="wp-caption alignright"><img loading="lazy" decoding="async" class=" wp-image-37633" src="https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2246-300x225.jpeg" alt="" width="390" height="292" srcset="https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2246-300x225.jpeg 300w, https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2246-1024x768.jpeg 1024w, https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2246-768x576.jpeg 768w, https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2246-1536x1152.jpeg 1536w, https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2246-2048x1536.jpeg 2048w" sizes="auto, (max-width: 390px) 100vw, 390px" /><figcaption id="caption-attachment-37633" class="wp-caption-text">From left to right: Jesse, John, Wendy, Mbili, David, Mike</figcaption></figure>
<p> </p>
<p class="p1"><em><strong>Core Description:</strong> Core description scientists will look at the sea floor sediments and underlying volcanic rocks to help figure out the history of the seamounts, from their initial volcanic formation to later covering by ocean sediments. By determining which types of rocks and sediments are found at the drill sites, the core loggers can understand how the volcanoes grew and became eroded with time.</em></p>
<ul class="ul1">
<li class="li1">Dr. David Buchs (Cardiff University)</li>
<li class="li1">Dr. Wendy Nelson (Townson University)</li>
<li class="li1">Jesse Scholpp (University of Tennessee)</li>
<li class="li1">Dr. John Shervais (Utah State University)</li>
<li class="li1">Mbili Tshiningayamwe (University of Namibia)</li>
<li class="li1">Dr. Mike Widdowson (University of Hull)</li>
<li>ONSHORE Dr. Rajneesh Bhutani (Pondicherry University)</li>
<li>ONSHORE Dr. Chun-Feng Li (Ocean University)</li>
</ul>
<p> </p>
<figure id="attachment_37643" aria-describedby="caption-attachment-37643" style="width: 169px" class="wp-caption alignleft"><img loading="lazy" decoding="async" class=" wp-image-37643" src="https://joidesresolution.org/wp-content/uploads/2022/01/Carote-IODP-2-214x300.jpg" alt="" width="169" height="237" srcset="https://joidesresolution.org/wp-content/uploads/2022/01/Carote-IODP-2-214x300.jpg 214w, https://joidesresolution.org/wp-content/uploads/2022/01/Carote-IODP-2.jpg 260w" sizes="auto, (max-width: 169px) 100vw, 169px" /><figcaption id="caption-attachment-37643" class="wp-caption-text">Giacomo Dalla Valle</figcaption></figure>
<p> </p>
<p> </p>
<p>FEATURED ONSHORE SCIENTIST: Dr. Giacomo Dalla Valle (ISMAR-Bologna). Giacomo is offering support to the part of the description of the sedimentary and volcanoclastic rocks, which are “above” the volcanic basement. Through the interpretation of photographs, and of their schematic logs he will help the colleagues on board in transcribing their observations and making their supporting figures.</p>
<p> </p>
<figure id="attachment_37634" aria-describedby="caption-attachment-37634" style="width: 286px" class="wp-caption alignright"><img loading="lazy" decoding="async" class=" wp-image-37634" src="https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2263-225x300.jpeg" alt="" width="286" height="381" srcset="https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2263-225x300.jpeg 225w, https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2263-768x1024.jpeg 768w, https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2263-1152x1536.jpeg 1152w, https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2263-1536x2048.jpeg 1536w, https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2263-scaled.jpeg 1920w" sizes="auto, (max-width: 286px) 100vw, 286px" /><figcaption id="caption-attachment-37634" class="wp-caption-text">From left to right: Aaron, Arianna</figcaption></figure>
<p> </p>
<p class="p1"><em><strong>Micropaleontology:</strong> Micropaleontologists will look at fossil content in cored sediments to reconstruct a depositional history the area. Specifically, calcareous nannofossils and foraminifera are great fossil groups for determining the age of the sediment, as well as examining the paleoenvironments, paleoclimate, and even paleoecology of a region. On a large scale, marine microfossil assemblages can be excellent indicators of major climatic shifts, responding to crucial climate perturbations such as the onset of the Antarctic circumpolar current (Eocene/Oligocene boundary) and the Paleocene Eocene Thermal Maximum.</em></p>
<ul class="ul1">
<li class="li1">Aaron Avery (Florida State University)</li>
<li class="li1">Arianna Del Gaudio (University of Graz)</li>
</ul>
<p> </p>
<p> </p>
<figure id="attachment_37636" aria-describedby="caption-attachment-37636" style="width: 421px" class="wp-caption alignright"><img loading="lazy" decoding="async" class=" wp-image-37636" src="https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2223-300x225.jpeg" alt="" width="421" height="316" srcset="https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2223-300x225.jpeg 300w, https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2223-1024x768.jpeg 1024w, https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2223-768x576.jpeg 768w, https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2223-1536x1152.jpeg 1536w, https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2223-2048x1536.jpeg 2048w" sizes="auto, (max-width: 421px) 100vw, 421px" /><figcaption id="caption-attachment-37636" class="wp-caption-text">From left to right: Harsha, Mark (pmag technician), Claire, Kevin</figcaption></figure>
<p class="p1"><em><strong>Paleomagnetism:</strong> Paleomagnetists study the magnetic field of the Earth recorded in ancient rocks to learn about the motion of the Earth and the evolution of its magnetic field. The known ages of regular reversals of the Earth’s magnetic field allow us to refine rock ages in conjunction with fossil and radiometric data. Studying magnetization directions on this expedition will help uncover how the Earths’ tectonic plates and deep interior moved relative to the Earth’s axis of rotation. Studying the strength of the magnetization in the volcanic rocks will also allow us to better understand the evolution of the Earth’s magnetic field and the liquid iron outer core that generates it.</em></p>
<ul class="ul1">
<li class="li1">Dr. Claire Carvallo (Sorbonne Université)</li>
<li class="li1">Kevin Gaastra (Rice University)</li>
<li class="li1">Dr. Sriharsha Thoram (University of Houston)</li>
<li class="li1">Dr. Sonia Tikoo (Stanford University)</li>
</ul>
<p> </p>
<figure id="attachment_37637" aria-describedby="caption-attachment-37637" style="width: 400px" class="wp-caption alignright"><img loading="lazy" decoding="async" class=" wp-image-37637" src="https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2242-300x225.jpeg" alt="" width="400" height="300" srcset="https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2242-300x225.jpeg 300w, https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2242-1024x768.jpeg 1024w, https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2242-768x576.jpeg 768w, https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2242-1536x1152.jpeg 1536w, https://joidesresolution.org/wp-content/uploads/2022/01/IMG_2242-2048x1536.jpeg 2048w" sizes="auto, (max-width: 400px) 100vw, 400px" /><figcaption id="caption-attachment-37637" class="wp-caption-text">From left to right: Yuhao, Seunghee, Yusuke</figcaption></figure>
<p class="p1"><em><strong>Geochemistry:</strong> Shipboard geochemists look into chemical compositions of various materials, including porewater, sediments, gases and igneous rocks we retrieved from drilling. The geochemical signatures of these materials can tell us about the chemical reactions occurred in water-sediment-rock systems. These reactions help us understand the environment these sediment/rocks are formed, their preservation conditions, as well as the material transport between different material components of the Earth. These geochemistry works lay the foundation for further studies onshore. Ultimately, we geochemists use these pieces of information to understand how various parts of the earth work and evolve.</em></p>
<ul class="ul1">
<li class="li1">Yuhao Dai (Lund University)</li>
<li class="li1">Dr. Seunghee Han (GwangJu Institute of Science and Technology)</li>
<li class="li1">Yusuke Kubota (Tokyo Institute of Technology)</li>
<li>ONSHORE Dr. Cornelia Class (Lamont Doherty Earth Observatory)</li>
<li>ONSHORE Dr. Stephan Homrighausen (GEOMAR)</li>
<li>ONSHORE Dr. Xiao-Jun Wang (Northwest University)</li>
</ul>
<p> </p>
<p>Mike and David are also… <em><strong>Volcanologists:</strong> Why does the expedition need volcanologists when we are drilling the sea floor…? What does a volcanologist do anyway – surely they should be looking at pointy, smoky volcanoes about to erupt..? Truth is volcanologists are a wide and varied group of scientists looking at a wide range of Earth’s phenomena that give rise to, and follow on from an eruptive event. There are many types of ‘volcanoes’ – the most common are not necessarily the pointy, smokey ones, but those that bubble and fizz, and erupt continuously on the ocean floor – so we very rarely see them, or are even aware they exist. These are part of the fiery ‘breathing’ of the planet, and ultimately are part of the story that drives the continents about the surface of our planet. So, this is the job of the volcanologists aboard our ship, to try and understand and build a story of the ancient seafloor volcanoes that we are about to drill – the cores we get will be like a story line telling us of the dying days of ancient sea volcanoes – our challenge is read their story from the rocks, and then tell it…</em></p>
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<title>To drill, or not to drill</title>
<link>https://joidesresolution.org/to-drill-or-not-to-drill/?utm_source=rss&utm_medium=rss&utm_campaign=to-drill-or-not-to-drill</link>
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<dc:creator><![CDATA[Maya Pincus]]></dc:creator>
<pubDate>Wed, 29 Dec 2021 17:28:50 +0000</pubDate>
<category><![CDATA[Biostratigraphy]]></category>
<category><![CDATA[Drilling]]></category>
<category><![CDATA[Expeditions]]></category>
<category><![CDATA[Paleomagnetism]]></category>
<category><![CDATA[Plate Tectonics]]></category>
<category><![CDATA[Sedimentology]]></category>
<category><![CDATA[Ship's Log]]></category>
<category><![CDATA[Volcanoes]]></category>
<category><![CDATA[debate]]></category>
<category><![CDATA[EXP391]]></category>
<category><![CDATA[hotspot]]></category>
<category><![CDATA[science]]></category>
<guid isPermaLink="false">https://joidesresolution.org/?p=37579</guid>
<description><![CDATA[The definitive guide to the drill sites of Expedition 391 In the original plan of IODP Expedition 391, six primary... <div class="read-more"><a class="excerpt-read-more" href="https://joidesresolution.org/to-drill-or-not-to-drill/" title="Continue reading To drill, or not to drill">Read more<i class="fa fa-angle-right"></i></a></div>]]></description>
<content:encoded><![CDATA[<h3>The definitive guide to the drill sites of Expedition 391</h3>
<figure id="attachment_37580" aria-describedby="caption-attachment-37580" style="width: 296px" class="wp-caption alignright"><img loading="lazy" decoding="async" class="wp-image-37580 size-medium" src="https://joidesresolution.org/wp-content/uploads/2021/12/Exp391-Drill-Sites-296x300.png" alt="" width="296" height="300" srcset="https://joidesresolution.org/wp-content/uploads/2021/12/Exp391-Drill-Sites-296x300.png 296w, https://joidesresolution.org/wp-content/uploads/2021/12/Exp391-Drill-Sites-1011x1024.png 1011w, https://joidesresolution.org/wp-content/uploads/2021/12/Exp391-Drill-Sites-768x778.png 768w, https://joidesresolution.org/wp-content/uploads/2021/12/Exp391-Drill-Sites.png 1074w" sizes="auto, (max-width: 296px) 100vw, 296px" /><figcaption id="caption-attachment-37580" class="wp-caption-text">Walvis Ridge bathymetry, fixed hotspot age models, previous drill sites, and proposed drill sites. Red circles = proposed primary drill sites. From the Exp391 Scientific Prospectus.</figcaption></figure>
<p class="p1">In the original plan of IODP Expedition 391, six primary drill sites were identified as locations to collect samples. Together, sediments and rocks from these six locations were to provide ample data to help scientists meet the objectives of the cruise. Our scientific goals are twofold: (1) to determine whether the volcanism of the Walvis Ridge hotspot track was influenced by one, two, or even three mantle plumes, and (2) to investigate whether evidence of true polar wander is preserved in the rocks of Walvis Ridge.<span class="Apple-converted-space"> </span></p>
<p class="p1">The story behind these six locations, and the order in which we were to reach them, is surprisingly fraught, with complications caused by territorial claims and even a solar eclipse. Now that our expedition has been delayed by more than two weeks, the story is even more complicated. It is no longer possible to reach all six sites in the time we have left. This means we need to make some sacrifices.</p>
<p class="p1">Over the past several days, the Expedition 391 science party has been meeting to discuss the benefits and disadvantages of each sampling location, to decide which sites are imperative to our objectives and which can be given up. The conversations have been based in science, and take into account several factors including the availability of usable preexisting data, maximizing recoverable core, and personal research projects.<span class="Apple-converted-space"> </span></p>
<p class="p1">This is a guide to each of the sites, in the order of the original plan to visit them. The descriptions are based on the original <a href="http://publications.iodp.org/scientific_prospectus/391/">Expedition 391 Scientific Prospectus</a>, as well as conversations with scientists in different fields of geoscience. By sharing this information with you, we are hoping to make our thinking transparent, and invite you to participate in the science with us as we do our best to decide where to sample.</p>
<p> </p>
<figure id="attachment_37589" aria-describedby="caption-attachment-37589" style="width: 263px" class="wp-caption alignleft"><img loading="lazy" decoding="async" class="wp-image-37589 " src="https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0629-225x300.jpeg" alt="" width="263" height="351" srcset="https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0629-225x300.jpeg 225w, https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0629-768x1024.jpeg 768w, https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0629-1152x1536.jpeg 1152w, https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0629-1536x2048.jpeg 1536w, https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0629-scaled.jpeg 1920w" sizes="auto, (max-width: 263px) 100vw, 263px" /><figcaption id="caption-attachment-37589" class="wp-caption-text">Paleontologist Arianna del Gaudio defends her choice of a site with a thick sediment package. From Maya Pincus.</figcaption></figure>
<p class="p1"><strong>VB-12A: </strong>This site is located on the southeast side of Valdivia Bank. It has a seafloor depth of 3667 meters below the surface. In this location, the sediment is 293 meters thick above the volcanic basement rock. The drilling plan for this site is to use just one bit, which will allow us to penetrate 100 m into the basement.<span class="Apple-converted-space"> </span></p>
<p class="p1">This site is preferred by our micropaleontologists because it has a thick layer of sediments, which means we will be able to find plenty of fossils that will allow us to determine the ages of the rock layers, and will also give us a more thorough record of paleoclimate changes over time. A thick layer of sediments is important also due to our drilling process. Since this expedition is focused primarily on lava flows, which produce hard igneous rock, we will be utilizing rotary core barrel (RCB) drilling. The thicker the sediment layer, the more likely it is that the lower sediments will be lithified, and therefore more likely to be recovered by the RCB process.<span class="Apple-converted-space"> </span></p>
<p class="p1">VB-12A is also the preferred site for paleomagnetists, who are here to interrogate rocks of the Walvis Ridge to calculate a precise paleolatitude of the mantle plume hotspot that formed the ridge. This paleolatitude can be compared to preexisting models of hotspot migration and true polar wander, to give more insight into the processes that led to paloelatitude shifts. This site is ideal for this aspect of the investigation because it formed ~85 million years ago, which is when a true polar wander event is hypothesized to have occurred.</p>
<p> </p>
<p class="p1"><strong>FR-1B: </strong>This site is the northernmost site of the expedition, located in a region known as Frio Ridge. It has a seafloor depth of 3259 meters below the sea surface, and a sediment thickness of 171 m. With an age of ~100 million years, it is the oldest site. The original plan was for this to be a two-bit hole, allowing us to drill 250 m into the igneous basement.</p>
<p class="p1">The Frio Ridge site is scientifically interesting because it is the closest site to the Namibian continental shelf. For micropaleontologists, this means that there may be both marine and terrestrial inputs to the fossil record. For geochemists, the possible influence from continental sources provides an opportunity to learn more about the long term processes that determine mantle composition and behavior.</p>
<p class="p1">Previous data from this region indicate that, though the sediment package is relatively thin, it spans the greatest length of time. A wide age range in these sediments will allow scientists to develop a high-resolution interpretation of changes to ocean conditions and climate over time.</p>
<figure id="attachment_37592" aria-describedby="caption-attachment-37592" style="width: 634px" class="wp-caption aligncenter"><img loading="lazy" decoding="async" class="wp-image-37592 " src="https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0733-2-300x141.jpeg" alt="" width="634" height="298" srcset="https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0733-2-300x141.jpeg 300w, https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0733-2-1024x480.jpeg 1024w, https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0733-2-768x360.jpeg 768w, https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0733-2-1536x720.jpeg 1536w, https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0733-2-2048x960.jpeg 2048w" sizes="auto, (max-width: 634px) 100vw, 634px" /><figcaption id="caption-attachment-37592" class="wp-caption-text">The conversation continued even as we geared up for Christmas. From Maya Pincus.</figcaption></figure>
<p> </p>
<p class="p1"><strong>VB-14A: </strong>This site is located on the western side of the Valdivia Bank, with a seafloor depth of 3046 meters below the sea surface. The sediment layer is 310 m thick. This site is also a one-bit site, allowing for recovery of up to 100 m of igneous basement rocks.</p>
<p class="p1">Given that this site is also on Valdivia Bank, it is important to the story of the strange morphology of the Walvis Ridge. We know that a mantle plume was involved in its formation, but the story is complicated by the fact that it is not a “string of pearls” seamount chain like classic hotspot tracks.</p>
<p class="p1">Studying the paleomagnetism and the geochemistry of the rocks from this location will help decipher the elusive history of this unusual oceanic plateau. The more data we have, the more likely we will be able to determine the extent of interaction between the Mid-Atlantic Ridge and the mantle plume that formed the Walvis Ridge. This will also provide evidence to test the hypothesis that the ridge formed contemporaneously with a microplate, which would have affected volcanism in the region.</p>
<p> </p>
<figure id="attachment_37594" aria-describedby="caption-attachment-37594" style="width: 300px" class="wp-caption alignleft"><img loading="lazy" decoding="async" class="size-medium wp-image-37594" src="https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0620-300x225.jpeg" alt="" width="300" height="225" srcset="https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0620-300x225.jpeg 300w, https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0620-1024x768.jpeg 1024w, https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0620-768x576.jpeg 768w, https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0620-1536x1152.jpeg 1536w, https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0620-2048x1536.jpeg 2048w" sizes="auto, (max-width: 300px) 100vw, 300px" /><figcaption id="caption-attachment-37594" class="wp-caption-text">It is not always easy to coordinate between the individual plans of over twenty scientists. From Maya Pincus.</figcaption></figure>
<p class="p1"><strong>TT-4A: </strong>This site is part of what we refer to as the Tristan track, which is the chain of seamounts that stretches from the southern tip of Valdivia Bank to the Tristan da Cunha islands. The site has a seafloor depth of 3465 meters below the sea surface, and a sediment thickness of 152 m. We will also limit our drilling to one bit at this location, so we aim to recover 100 m of volcanic basement from this site.</p>
<p class="p1">Sampling the Tristan track is crucial to our goal of determining the degree to which the Walvis Ridge is geochemically zoned. The data from this site, along with data from CT-4A and GT-4A, will show how many distinct mantle plume sources contributed to the formation of the three seamount tracks in the south of the Walvis Ridge.</p>
<p class="p1">Geochemical analyses have already been carried out on samples dredged from the sea floor at several locations along the Tristan track. However, seafloor dredging is a comparatively imprecise method, as there is little control over sample selection. Drilling will allow us to collect data to determine how the geochemistry at one location has changed over time, which will provide valuable insight into the dynamic behavior of the plume or plumes that formed the Walvis Ridge.</p>
<p> </p>
<figure id="attachment_37588" aria-describedby="caption-attachment-37588" style="width: 262px" class="wp-caption alignright"><img loading="lazy" decoding="async" class=" wp-image-37588" src="https://joidesresolution.org/wp-content/uploads/2021/12/IMG_1030-225x300.jpeg" alt="" width="262" height="350" srcset="https://joidesresolution.org/wp-content/uploads/2021/12/IMG_1030-225x300.jpeg 225w, https://joidesresolution.org/wp-content/uploads/2021/12/IMG_1030-768x1024.jpeg 768w, https://joidesresolution.org/wp-content/uploads/2021/12/IMG_1030-1152x1536.jpeg 1152w, https://joidesresolution.org/wp-content/uploads/2021/12/IMG_1030-1536x2048.jpeg 1536w, https://joidesresolution.org/wp-content/uploads/2021/12/IMG_1030-scaled.jpeg 1920w" sizes="auto, (max-width: 262px) 100vw, 262px" /><figcaption id="caption-attachment-37588" class="wp-caption-text">Paleomagnetist Dr. Sonia Tikoo explains the geological importance of her preferred site. From Maya Pincus.</figcaption></figure>
<p class="p1"><strong>CT-4A: </strong>This site is located in the central track, the chain of seamounts between the Tristan track and the Gough track. It is our youngest site, and with a seafloor depth of 4436 meters below the sea surface, it is also our deepest site. The sediment thickness at this location is 278 m. This is also intended to be a two-bit hole, allowing for drill penetration up to 250 m below the seafloor.</p>
<p class="p1">Samples from this location are considered by many to be the most important in answering the question of the mantle source that contributed to the formation of the Walvis Ridge. Preexisting data indicate that the Tristan track and the Gough track are geochemically distinct, which means that they come from two unique mantle sources. What we do not yet know is the origin of this central track. Was it formed by a third mantle plume in the region? Does it represent some sort of mixing between the Tristan plume source and the Gough plume source? Answering these questions will help scientists to develop more detailed models for overall mantle behavior.</p>
<p class="p1">This site is also important to paleomagnetists, as it formed around the same time as the bend in the Hawaii-Emperor Chain (read more about this <a href="https://joidesresolution.org/not-all-hotspots-who-wander-are-lost-exp391-science-objectives-part-2/">here</a>). Paleolatitude interpretations of the rocks at this site will help tell the story of true polar wander in the early Cenozoic.</p>
<p> </p>
<figure id="attachment_37602" aria-describedby="caption-attachment-37602" style="width: 225px" class="wp-caption alignleft"><img loading="lazy" decoding="async" class="size-medium wp-image-37602" src="https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0722-225x300.jpeg" alt="" width="225" height="300" srcset="https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0722-225x300.jpeg 225w, https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0722-768x1024.jpeg 768w, https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0722-1152x1536.jpeg 1152w, https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0722-1536x2048.jpeg 1536w, https://joidesresolution.org/wp-content/uploads/2021/12/IMG_0722-scaled.jpeg 1920w" sizes="auto, (max-width: 225px) 100vw, 225px" /><figcaption id="caption-attachment-37602" class="wp-caption-text">Namibian Observer Dr. Mbili Tshiningayamwe weighs in. From Maya Pincus.</figcaption></figure>
<p class="p1"><strong>GT-4A: </strong>This site is located along the Gough track, the chain of seamounts that spans the southern tip of the Valdivia Bank to Gough Island. It has a seafloor depth of 2370 meters below the sea surface, and a layer of sediments 302 m thick. As a one-bit hole, we plan to recover up to 100 m of igneous rock at this location.</p>
<p class="p1">Along with samples from TT-4A and CT-4A, rocks from this location will provide the data necessary to interpret the mantle plume behavior that resulted in the three chains of hotspot seamounts rather than just one track. As one end-member in geochemical story (with the Tristan track as the other end-member), comparative analyses will help us interpret the geologic history of the central track.</p>
<p class="p3">Several dredge samples were also collected from along the Gough track, meaning that geochemical data is available, though it lacks the high resolution that is provided by a drill core. This site is also the source of concern to our scientists interested in sediments, as seismic data indicate that faulting in the area caused sediments to slump. This means that the original order of deposition has been disturbed, which will complicate the interpretation of the layers.</p>
<p> </p>
<p style="text-align: center;">Tune into our social media accounts to follow our journey and see which sites we decide to drill!</p>
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<title>Not all [hotspots] who wander are lost (Exp391 Science Objectives, Part 2)</title>
<link>https://joidesresolution.org/not-all-hotspots-who-wander-are-lost-exp391-science-objectives-part-2/?utm_source=rss&utm_medium=rss&utm_campaign=not-all-hotspots-who-wander-are-lost-exp391-science-objectives-part-2</link>
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<dc:creator><![CDATA[Maya Pincus]]></dc:creator>
<pubDate>Mon, 20 Dec 2021 19:13:05 +0000</pubDate>
<category><![CDATA[Drilling]]></category>
<category><![CDATA[Education]]></category>
<category><![CDATA[Expeditions]]></category>
<category><![CDATA[History of Earth]]></category>
<category><![CDATA[Paleomagnetism]]></category>
<category><![CDATA[Plate Tectonics]]></category>
<category><![CDATA[Volcanoes]]></category>
<category><![CDATA[EXP391]]></category>
<category><![CDATA[hotspot]]></category>
<category><![CDATA[magnetic field]]></category>
<category><![CDATA[mantle plume]]></category>
<category><![CDATA[paleolatitude]]></category>
<category><![CDATA[true polar wander]]></category>
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<description><![CDATA[This post was written by Maya and edited by JR scientist Kevin Gaastra. Kevin is a fifth year PhD student... <div class="read-more"><a class="excerpt-read-more" href="https://joidesresolution.org/not-all-hotspots-who-wander-are-lost-exp391-science-objectives-part-2/" title="Continue reading Not all [hotspots] who wander are lost (Exp391 Science Objectives, Part 2)">Read more<i class="fa fa-angle-right"></i></a></div>]]></description>
<content:encoded><![CDATA[<p><em>This post was written by Maya and edited by JR scientist Kevin Gaastra. Kevin is a fifth year PhD student studying tectonics and paleomagnetism at Rice University. When the landscape provides, he can be found snow skiing down some mountain in Tahoe.</em></p>
<p class="p1" style="text-align: left;">When Professor Will Sager of the University of Houston announced that he would be going to Walvis Ridge to investigate true polar wander, a topic of of special significance, there was much talk and excitement within the scientific community.</p>
<p class="p1">The concept of true polar wander is scientifically rich, and somewhat peculiar, and has been a wonder of paleolatitude investigations for many years. But before we learn more about this fascinating concept, and see how it connects to the Walvis Ridge, we must begin again by visiting the Hawaiian islands and Emperor seamount chain.<span class="Apple-converted-space"> </span></p>
<figure id="attachment_37559" aria-describedby="caption-attachment-37559" style="width: 437px" class="wp-caption alignleft"><img loading="lazy" decoding="async" class="wp-image-37559 " src="https://joidesresolution.org/wp-content/uploads/2021/12/Hawaiian-Emperor-Chain-1-300x194.png" alt="" width="437" height="283" srcset="https://joidesresolution.org/wp-content/uploads/2021/12/Hawaiian-Emperor-Chain-1-300x194.png 300w, https://joidesresolution.org/wp-content/uploads/2021/12/Hawaiian-Emperor-Chain-1-1024x662.png 1024w, https://joidesresolution.org/wp-content/uploads/2021/12/Hawaiian-Emperor-Chain-1-768x496.png 768w, https://joidesresolution.org/wp-content/uploads/2021/12/Hawaiian-Emperor-Chain-1-1536x992.png 1536w, https://joidesresolution.org/wp-content/uploads/2021/12/Hawaiian-Emperor-Chain-1.png 1582w" sizes="auto, (max-width: 437px) 100vw, 437px" /><figcaption id="caption-attachment-37559" class="wp-caption-text">The Hawaiian-Emperor hotspot track is distinguished by the bend between the Hawaiian Ridge and the Emperor seamount chain. From National Geophysical Data Center/USGS.</figcaption></figure>
<p class="p1">Due to the stark differences in their orientation, we refer to the geographic features as two separate groups: the Hawaiian islands and ridge, and the Emperor seamount chain. However, these chains of islands and underwater mountains are linked by more than proximity: the age progression that starts with the currently active volcanic island of Hawaii continues not just along the Hawaiian ridge, but also through each of the seamounts of the Emperor chain. This indicates that the same mantle plume formed both mountain chains, and therefore the same hotspot has been active in the Pacific since the formation of the first Emperor island 80 million years ago.<span class="Apple-converted-space"> </span></p>
<p class="p1">In the <a href="https://joidesresolution.org/hotspot-whodunnit-exp391-science-objectives-part-1/">previous post</a>, we talked about the general mechanism for the formation of hotspot tracks: a solid but fluid plume of hot, buoyant mantle material rises towards the crust where it melts the overlying rock to form an active volcano. The reason we do not see just one ever-growing volcano is that Earth’s surface is composed of several rigid sections, called tectonic plates, that move slowly. As a tectonic plate moves over the hotspot, the original volcano is carried away and a new one forms in its place.</p>
<figure id="attachment_37556" aria-describedby="caption-attachment-37556" style="width: 452px" class="wp-caption alignright"><img loading="lazy" decoding="async" class=" wp-image-37556" src="https://joidesresolution.org/wp-content/uploads/2021/12/hotspot-formation-300x154.jpg" alt="" width="452" height="232" srcset="https://joidesresolution.org/wp-content/uploads/2021/12/hotspot-formation-300x154.jpg 300w, https://joidesresolution.org/wp-content/uploads/2021/12/hotspot-formation-1024x527.jpg 1024w, https://joidesresolution.org/wp-content/uploads/2021/12/hotspot-formation-768x395.jpg 768w, https://joidesresolution.org/wp-content/uploads/2021/12/hotspot-formation.jpg 1100w" sizes="auto, (max-width: 452px) 100vw, 452px" /><figcaption id="caption-attachment-37556" class="wp-caption-text">Model of hot-spot volcanism thought to explain the formation of oceanic plateaus and the volcanic islands associated with these features. A. Rising mantle plume. B. Outpourings of basalt generate the oceanic plateau. C. Less voluminous activity produces a linear volcanic chain on the seafloor. From Tasa Graphics, via AGU blog</figcaption></figure>
<p class="p1">In theory, this is a very straightforward process, and one that can be a hoard of information about the movement of Earth’s tectonic plates and the convective flow of Earth’s mantle. The problem is that this hoard, like all hoards, comes with a dragon that makes things a bit complicated.</p>
<p class="p1">In this case, our dragon is the bend in the chain. What could have caused the volcanic islands to suddenly be carried off in a different direction? Perhaps the most straightforward explanation is that the Pacific Plate changed its direction of movement starting ~45-50 million years ago. It had originally been moving towards the north, but something caused it to change direction and head towards the west.<span class="Apple-converted-space"> </span></p>
<p class="p1">Though this explanation is simple, unfortunately not all the data collected from these rocks support this hypothesis. We must now delve deeper into the science, to understand a concept called paleolatitude. From Greek “palaios” meaning old, the term paleolatitude refers to the fact that, through the movement of Earth’s tectonic plates, many of the rocks on Earth’s surface are in a location that is different from where they formed. When scientists use analyses to determine where on Earth the rocks formed, they are determining paleolatitude.</p>
<p class="p1">There are several ways that scientists can determine the paleolatitude of geological formations. In the case of the Hawaiian-Emperor seamounts, scientists were able to study the signature of Earth’s magnetic field in the rocks to match them, much like one matches a puzzle piece, to the global map of field lines.</p>
<figure id="attachment_37560" aria-describedby="caption-attachment-37560" style="width: 415px" class="wp-caption alignleft"><img loading="lazy" decoding="async" class=" wp-image-37560" src="https://joidesresolution.org/wp-content/uploads/2021/12/Rock-Magnetization-300x289.png" alt="" width="415" height="400" srcset="https://joidesresolution.org/wp-content/uploads/2021/12/Rock-Magnetization-300x289.png 300w, https://joidesresolution.org/wp-content/uploads/2021/12/Rock-Magnetization-1024x987.png 1024w, https://joidesresolution.org/wp-content/uploads/2021/12/Rock-Magnetization-768x740.png 768w, https://joidesresolution.org/wp-content/uploads/2021/12/Rock-Magnetization.png 1104w" sizes="auto, (max-width: 415px) 100vw, 415px" /><figcaption id="caption-attachment-37560" class="wp-caption-text">Illustration of how rocks become magnetized. As lava cools, the solidifying rock acquires a magnetization, which is aligned to Earth’s magnetic field. From Roberts and Turner, 2013.</figcaption></figure>
<p class="p1">Here’s how it works: Many volcanic rocks have a small concentration of magnetic minerals inside them. Before the rocks solidify, when the lava is still liquid, the magnetic minerals are able to move around to align themselves with Earth’s magnetic field. This is similar to what it looks like when the needle of a compass orients itself. As the lava cools and hardens, the minerals become trapped in that orientation, preserving an image of what Earth’s magnetic field looks like in the area they formed. As long as the rock remains unaltered by remagnetizing processes (ex: melting, lightning strike), the magnetic minerals are preserved in the same orientation in which they formed, no matter how much that rock is transported by erosion or tectonic activity. When scientists perform complex analyses, they are able to interpret the magnetization of the rock and determine the latitude where it formed.</p>
<p class="p1">When paleolatitude measurements are used to reconstruct the tectonic motion of rocks from the Hawaiian-Emperor chain and surrounding tectonic plates, the paleolatitudes indicate that Hawaii must have moved south, despite the plate moving north.</p>
<p class="p1">Thus, a second hypothesis was proposed. Historically, geologists had hypothesized that mantle plumes were fixed in place under a moving plate, creating a stationary hotspot. What if instead the location of the hotspot changed over time? This concept became known as mantle plume migration.</p>
<p class="p1">Could a wandering hotspot be responsible for the unusual geography of the Hawaiian-Emperor chain? To answer this question, scientists developed detailed computer models to simulate all possible combinations of plate motion and hotspot migration that could have caused the bend in the chain. Though many different scientists modeled several different combinations of plate motion and plume migration, they struggled to find a solution that accurately mapped the movement in a way that agreed with the measured ages and paleolatitudes of the seamounts.</p>
<p class="p1">One more possibility can account for the morphology and paleolatitude measurements of these surprising seamounts: a phenomenon known as true polar wander. This is an idea that can be very hard to wrap your head around, so we’ll go slow. We’ll start with something basic: Earth is spinning. This is what gives us night and day and why we need time zones. Every spinning object has an axis, which is an invisible line that represents the center that the object is spinning around. Earth’s axis of rotation runs between the North Pole and the South Pole.</p>
<p class="p1">When an object is homogenous and rigid, there is nothing to affect the spin. However, if an object is NOT homogeneous, irregularities in its form can cause the spinning object to reorient around a new axis. The video below, created by NASA scientists, demonstrates the changing spin axis of a non-homogeneous rigid object.</p>
<div style="width: 1200px;" class="wp-video"><video class="wp-video-shortcode" id="video-37553-3" width="1200" height="675" preload="metadata" controls="controls"><source type="video/mp4" src="https://joidesresolution.org/wp-content/uploads/2021/12/Dancing-T-handle-in-zero-g-HD-1n-HMSCDYtM.mp4?_=3" /><a href="https://joidesresolution.org/wp-content/uploads/2021/12/Dancing-T-handle-in-zero-g-HD-1n-HMSCDYtM.mp4">https://joidesresolution.org/wp-content/uploads/2021/12/Dancing-T-handle-in-zero-g-HD-1n-HMSCDYtM.mp4</a></video></div>
<p>Earth is also irregular. The surface of our planet is irregular, with mountains in some places and oceans in others. Middle Earth (in this case, the mantle) is also irregular: it is hot and buoyant in some places, and cooler and more dense in others. If an object is fluid, the internal motions of the fluid can change the object’s spin. Though the Earth’s mantle is solid, it flows like a liquid over millions of years and can alter Earth’s rotation.</p>
<p>This video, also created by NASA, first demonstrates the stable and consistent spin of rigid, more-or-less homogeneous objects. Beginning at 0:36, it is shown that the spin of fluid objects reorients over time.</p>
<div style="width: 960px;" class="wp-video"><video class="wp-video-shortcode" id="video-37553-4" width="960" height="540" preload="metadata" controls="controls"><source type="video/mp4" src="https://joidesresolution.org/wp-content/uploads/2021/12/Rotating-Objects-in-Microgravity-e.mp4?_=4" /><a href="https://joidesresolution.org/wp-content/uploads/2021/12/Rotating-Objects-in-Microgravity-e.mp4">https://joidesresolution.org/wp-content/uploads/2021/12/Rotating-Objects-in-Microgravity-e.mp4</a></video></div>
<p> </p>
<p class="p1">Scientists have hypothesized that the physical irregularities moving in our planet have caused the entire surface to shift relative to its axis of spin. This would cause the paleolatitude of EVERYTHING to shift. Data indicate that the Hawaii-Emperor hotspot shifted ~12º southward. If true polar wander really did occur, we should expect to see a corresponding shift in other landmasses.</p>
<p class="p1">Conveniently, the Walvis Ridge is located just about on the opposite side of the world from the Hawaii-Emperor chain. If polar wander is truly the explanation for the confusing paleolatitude measurements of the Hawaiian and Emperor seamounts, then we can expect to see similar data in the Walvis Ridge: as the Hawaiian-Emperor chain shifted southward, the Walvis Ridge migrated toward the north.</p>
<p class="p1">This is what the scientists of IODP Expedition 391 are here to investigate. By collecting core samples from several locations along the Walvis Ridge, we can determine if crustal material on both sides of the Earth shifted comparably. If we see a corresponding paleolatitude shift to the north in rocks from the Walvis Ridge, and connect it to the shift to the south of the Hawaiian-Emperor chain, we can infer that there was a shift of all crustal material, which would indicate that true polar wander did occur.</p>
<p class="p1">And so, loading our drill bits and core barrels, we set off, seeking a path that would bring us to the underwater hills of Walvis Ridge, down into the land of hotspots.</p>
<p><em>Featured photo: Victor C. Tsai (left); Goldreich and Toomre, 1969 (right).</em></p>
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<title>HOTSPOT WHODUNNIT (EXP391 Science Objectives, Part 1)</title>
<link>https://joidesresolution.org/hotspot-whodunnit-exp391-science-objectives-part-1/?utm_source=rss&utm_medium=rss&utm_campaign=hotspot-whodunnit-exp391-science-objectives-part-1</link>
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<dc:creator><![CDATA[Maya Pincus]]></dc:creator>
<pubDate>Fri, 10 Dec 2021 12:10:53 +0000</pubDate>
<category><![CDATA[Drilling]]></category>
<category><![CDATA[Education]]></category>
<category><![CDATA[Expeditions]]></category>
<category><![CDATA[Geochemistry]]></category>
<category><![CDATA[Plate Tectonics]]></category>
<category><![CDATA[Volcanoes]]></category>
<category><![CDATA[#HotspotWhodunnit]]></category>
<category><![CDATA[EXP391]]></category>
<category><![CDATA[hotspot]]></category>
<category><![CDATA[mantle]]></category>
<category><![CDATA[mantle plume]]></category>
<category><![CDATA[plate tectonics]]></category>
<guid isPermaLink="false">https://joidesresolution.org/?p=37529</guid>
<description><![CDATA[If you’ve spent any time looking at satellite images of Earth (for example, Google Maps), you probably noticed that the... <div class="read-more"><a class="excerpt-read-more" href="https://joidesresolution.org/hotspot-whodunnit-exp391-science-objectives-part-1/" title="Continue reading HOTSPOT WHODUNNIT (EXP391 Science Objectives, Part 1)">Read more<i class="fa fa-angle-right"></i></a></div>]]></description>
<content:encoded><![CDATA[<p>If you’ve spent any time looking at satellite images of Earth (for example, Google Maps), you probably noticed that the oceans are dotted with what appears to be lines of islands and underwater mountains. These geological features, known as hotspot tracks, are beautifully exemplified by the islands of Hawaii and the Louisville Ridge. Referred to as “string-of-pearl” hotspots track by Expedition 391 co-chief scientists Dr. Kaj Hoernle and Dr. Will Sager, these chains of ocean volcanoes show a very clear pattern that matches nicely with how scientists understand hotspots to form.</p>
<figure id="attachment_37531" aria-describedby="caption-attachment-37531" style="width: 641px" class="wp-caption aligncenter"><img loading="lazy" decoding="async" class="wp-image-37531" src="https://joidesresolution.org/wp-content/uploads/2021/12/string-of-pearl-hotspots-300x102.png" alt="classic "string of pearl" hotspot tracks" width="641" height="218" srcset="https://joidesresolution.org/wp-content/uploads/2021/12/string-of-pearl-hotspots-300x102.png 300w, https://joidesresolution.org/wp-content/uploads/2021/12/string-of-pearl-hotspots-1024x347.png 1024w, https://joidesresolution.org/wp-content/uploads/2021/12/string-of-pearl-hotspots-768x260.png 768w, https://joidesresolution.org/wp-content/uploads/2021/12/string-of-pearl-hotspots-1536x520.png 1536w, https://joidesresolution.org/wp-content/uploads/2021/12/string-of-pearl-hotspots-2048x693.png 2048w" sizes="auto, (max-width: 641px) 100vw, 641px" /><figcaption id="caption-attachment-37531" class="wp-caption-text">These bathymetric maps show off three classic hotspot tracks: Emperor seamount chain and Hawaiian islands (left), and Louisville Ridge (right). From National Geophysical Data Center/USGS (left) and NOAA (right).</figcaption></figure>
<p class="p1">We live on Earth’s crust, the outermost layer. Below our feet, between about 30 and 70 km down on land, lies the upper mantle (also called the asthenosphere). Scientists refer to the texture of this layer as “plastic” because even though it’s technically solid, it has the ability to flow. Though there is still a lot we DON’T know about Earth’s interior, observations of how earthquake waves travel through the mantle make it clear that the layer is quite heterogeneous. Some regions of the mantle are much warmer than the rest, making them less dense and more buoyant. These hot, buoyant regions of mantle material, known as mantle plumes, rise up until they reach the base of the crust, where they cause melting and therefore the formation of a volcano. Over time, the tectonic plate located above the mantle plume moves, carrying the original volcano away and allowing a new, younger volcano to form in its place. Over tens of millions of years, a chain of “age-progressive” volcanoes is produced: the farther you go from the location of the mantle plume, the older the volcanoes get.</p>
<figure id="attachment_37534" aria-describedby="caption-attachment-37534" style="width: 306px" class="wp-caption alignleft"><img loading="lazy" decoding="async" class=" wp-image-37534" src="https://joidesresolution.org/wp-content/uploads/2021/12/Walvis-Ridge-300x232.png" alt="the highly atypical Walvis Ridge" width="306" height="237" srcset="https://joidesresolution.org/wp-content/uploads/2021/12/Walvis-Ridge-300x232.png 300w, https://joidesresolution.org/wp-content/uploads/2021/12/Walvis-Ridge-1024x793.png 1024w, https://joidesresolution.org/wp-content/uploads/2021/12/Walvis-Ridge-768x595.png 768w, https://joidesresolution.org/wp-content/uploads/2021/12/Walvis-Ridge.png 1180w" sizes="auto, (max-width: 306px) 100vw, 306px" /><figcaption id="caption-attachment-37534" class="wp-caption-text">The Walvis Ridge is a highly unusual hotspot track, with a broad plateau to the northeast and three distinct chains of seamounts to the southwest. From NOAA.</figcaption></figure>
<p class="p1">Now, let’s take a look at the Walvis Ridge. It can’t be any more different than those string of pearl hotspot tracks… So what’s going on? To the northeast, you see that very wide underwater plateau. That’s called the Valdivia Bank. To the southwest, the seamounts branch into three distinct tracks, which we refer to colloquially as the Trident. Even the most basic visual inspection shows us that something strange is going on here. Thus begins our mystery: the HOTSPOT WHODUNNIT!</p>
<p class="p1">Even the most novice detective knows that the first step to solving a mystery is to start with the clues you already have. First, some nomenclature. The band of elevated sea floor that we are investigating is called the Walvis Ridge.</p>
<figure id="attachment_37536" aria-describedby="caption-attachment-37536" style="width: 430px" class="wp-caption alignright"><img loading="lazy" decoding="async" class="wp-image-37536" src="https://joidesresolution.org/wp-content/uploads/2021/12/Tristan-and-Gough-islands-300x171.png" alt="Tristan da Cunha and Gough Islands" width="430" height="245" srcset="https://joidesresolution.org/wp-content/uploads/2021/12/Tristan-and-Gough-islands-300x171.png 300w, https://joidesresolution.org/wp-content/uploads/2021/12/Tristan-and-Gough-islands-1024x583.png 1024w, https://joidesresolution.org/wp-content/uploads/2021/12/Tristan-and-Gough-islands-768x438.png 768w, https://joidesresolution.org/wp-content/uploads/2021/12/Tristan-and-Gough-islands-1536x875.png 1536w, https://joidesresolution.org/wp-content/uploads/2021/12/Tristan-and-Gough-islands-2048x1167.png 2048w" sizes="auto, (max-width: 430px) 100vw, 430px" /><figcaption id="caption-attachment-37536" class="wp-caption-text">The Tristan da Cunha and Gough islands are each located at the end of one of the prongs of the Walvis Ridge “trident”. From Google Earth.</figcaption></figure>
<p class="p1">The hotspot involved in its formation is the Tristan-Gough hotspot, named for two volcanic islands in the southern Atlantic ocean. As you can see below, the Tristan da Cunha islands are located at the end of one prong of the Trident, and Gough island is located at the end of another. Just invoking the names of these islands brings us to our first question: If the islands are so far apart, and located on different prongs of the Trident, can we really say that there is only one hotspot? What if there are two, or even three mantle plumes responsible for this complex bathymetry?</p>
<p class="p1">That brings us to our second clue, some of the data that we do have. Given that this hotspot is so unusual (in fact, Dr. Hoernle refers to it as one of “the most complicated hotspot tracks on Earth”), we are by no means the first group of scientists trying to figure out what’s going on.</p>
<figure id="attachment_37537" aria-describedby="caption-attachment-37537" style="width: 433px" class="wp-caption alignright"><img loading="lazy" decoding="async" class=" wp-image-37537" src="https://joidesresolution.org/wp-content/uploads/2021/12/T-G-age-data-300x171.png" alt="age data from the Tristan-Gough hotspot track" width="433" height="247" srcset="https://joidesresolution.org/wp-content/uploads/2021/12/T-G-age-data-300x171.png 300w, https://joidesresolution.org/wp-content/uploads/2021/12/T-G-age-data-1024x583.png 1024w, https://joidesresolution.org/wp-content/uploads/2021/12/T-G-age-data-768x437.png 768w, https://joidesresolution.org/wp-content/uploads/2021/12/T-G-age-data-1536x875.png 1536w, https://joidesresolution.org/wp-content/uploads/2021/12/T-G-age-data-2048x1166.png 2048w" sizes="auto, (max-width: 433px) 100vw, 433px" /><figcaption id="caption-attachment-37537" class="wp-caption-text">Age data from the Tristan-Gough hotspot track. The linear trends in the data indicate classic hotspot age progression. Data sources shown in figure; approximate lines drawn for this post.</figcaption></figure>
<p class="p1">Earlier you read about how one sure-fire indicator of a conventional hotspot is the progression of increasing age with distance from the hotspot. When plotted on a graph, that would show the data lined up, with a clear relationship between age and distance from the active volcano. Here’s what Walvis Ridge data give us: not one, but two lines on the age-distance plot. Could this be the fingerprint pointing toward a two-plume explanation? Let’s see what the rest of the evidence suggests.</p>
<p class="p1">Another way that scientists learn about rocks is through something called geochemistry. This is a very broad term that means analyzing the chemical compositions of the rocks and the minerals that comprise them.</p>
<p class="p1">One application of geochemistry is determining the ages of rocks like we just talked about. Another way that geochemistry can help us here is that it can indicate if rocks found in different locations share a history. If two samples show similar geochemical signatures, it is possible to infer that they came from the same source.</p>
<figure id="attachment_37538" aria-describedby="caption-attachment-37538" style="width: 494px" class="wp-caption alignleft"><img loading="lazy" decoding="async" class=" wp-image-37538" src="https://joidesresolution.org/wp-content/uploads/2021/12/T-G-Geochemistry-300x188.png" alt="the Tristan and Gough tracks are geochemically distinct" width="494" height="310" srcset="https://joidesresolution.org/wp-content/uploads/2021/12/T-G-Geochemistry-300x188.png 300w, https://joidesresolution.org/wp-content/uploads/2021/12/T-G-Geochemistry-1024x643.png 1024w, https://joidesresolution.org/wp-content/uploads/2021/12/T-G-Geochemistry-768x482.png 768w, https://joidesresolution.org/wp-content/uploads/2021/12/T-G-Geochemistry-1536x964.png 1536w, https://joidesresolution.org/wp-content/uploads/2021/12/T-G-Geochemistry-2048x1286.png 2048w" sizes="auto, (max-width: 494px) 100vw, 494px" /><figcaption id="caption-attachment-37538" class="wp-caption-text">Pb-isotope data indicate that rocks from the Tristan and Gough tracks fall into distinct geochemical groups. Samples from the Tristan track share characteristics with normal Mid-Atlantic Ridge basalts (Atlantic N-MORB).</figcaption></figure>
<p class="p1">Take this graph for example. On the axes we have ratios of different isotopes of the element lead (Pb). Isotopes are versions of the same element that have different amounts of neutrons, and therefore different atomic masses (as you follow along with our expedition, you’ll learn about many different things scientists can learn from isotopes). When the data are sorted this way, we can see that there are two distinct groups of points, which conveniently correspond to samples from the Tristan track and the Gough track respectively. This is could be the trace DNA evidence linking multiple mantle plumes to our volcanic islands.</p>
<p class="p1">With this information, we are hot on the case of figuring out the culprit of who formed Walvis Ridge and how they did it. But before we can conclude it was a two-plume mantle source interacting with a mid-ocean ridge (a la “It was Professor Plum in the Library with the Lead Pipe!”), we still need a few more clues.</p>
<p class="p1">Up to this point, we’ve only talked about the two outer prongs of the Trident. But what about the middle prong? Scientists have already found that it has a different geochemical signature than either the Tristan or the Gough track. Does this mean there is a third mantle plume as its source? Is there some sort of mixing between other two plumes tracking place before they reach the crust?</p>
<p class="p1">Don’t forget that the Trident is not the only strange thing about the Walvis Ridge… Why is Valdivia Bank such an abnormally broad oceanic plateau? Was it formed by the same mantle plume(s) that formed the Trident? What other processes were involved?</p>
<p class="p1">And the most important question of this mystery: How can we use what we learn about this unique hotspot track to better understand mantle processes and formation of new crust in general?</p>
<p class="p1">So we can see, this is a true HOTSPOT WHODUNNIT! Follow along with the detectives of Expedition 391 as they drill into the ocean floor to collect the clues they need to crack the case.</p>
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